Drawing press



Dec. 29, 1953 o. H. MAY 2,664,191

DRAWING PRESS Filed Feb. 28, 1949 2 Sheets-Sheet l Patented Dec. 29, 1953 DRAWING PRES S Otto Hermann May, Sehwabisch Gmund, Germany Application February 28, 1949, Serial No. 78,765

Claims priority, application Switzerland August 24, 1948 7 Claims.

This invention relates to drawing presses, and with regard to certain more specific features, to crank drawing presses such as are employed for forming long shells.

Present-day drawing presses have several disadvantages, the chief one of which is that drawing progresses at a decreasing drawing speed While the opposite is desirable in order to avoid a punching effect. A second disadvantage is that the pressure required at the beginning of the drawing operation is applied when the driving crank is in its most unfavorable position of greatest reactive lever arm, instead of at a minimum which may be gradually increased. A third disadvantage is that stroke of the press may be more than double the length of the shell, with the result that the ram first travels a substantial distance without doing any work. The end result of the stated disadvantages is a press that is unnecessarily large and expensive in construction, having an unnecessarily low production rate at a given forming speed. yMoreover, the former presses, as a result of the stated disadvantages, have a shorter useful life.

The present invention avoids the stated disadvantages without losing any of the other known advantages of drawing presses, by providing an auxiliary ram on the main ram. This auxiliary ram carries the punch and moves it parallel to the axis of motion of the main ram in such a manner that the auxiliary ram performs an independent return and forward stroke superimposed up-on the return and forward stroke of the main ram. The return and forward strokes of the auxiliary ram occur substantially during the retraction of the main ram.

The invention accordingly comprises the elewill be exemplified in the structures hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawings, in which one of various possible embodiments of the invention is illustrated,

Fig. 1 is a vertical section of parts of a drawing press illustrating the significant parts of the invention;

Fig. 2A is a fragmentary horizontal section taken on line 2-2 of Fig. 1; and

Fig. 3 is a curve illustrating the coordinated operations of the two rams, the relative positions of the rams with respect to one another and with respect to the drawing ring being also shown in coordination,

Similar reference characters indicate corresponding parts throughout the several views of the drawings.

Referring now more particularly to Figs. 1 and 2, there is shown at numeral I, a press frame which forms a guide 3 for a reciprocating main ram 5. The ram is reciprocated by the action of the usual crank 1 coupled through connecting rod 9, both being shown diagrammatically. A support |I is provided on the frame for a drawing ring I3. A support I5 is also provided for a vertical rack i1. Part of the frame I adjacent to the guide 3 is slotted at I9 to accommodate the motion of a bracket 2| which is bolted to the main ram 5. Thus as the crank 1 rotates anticlockwise, the main ram 5, together with the bracket 2l, is reciprocated up and down.

lnteriorly, the main ram 5 (which is hollow) is provided with a guide 2,3 for an auxiliary ram 25 which carries a punch 21. The auxiliary ram 25 is notched as shown at 29 to accommodate insertion of a latch 3| which passes through a suitable opening 33 in the side of the main ram 5. Elements 29, 3| and 33 constitute releasable coupling or holding means between the main ram 5 and the auxiliary ram 25. This latch is pinned to a bell-crank lever 35 which is pinned at 31 to the bracket 2|. A second bell-crank lever 39 is pinned at rIII to the bracket 2|. The bell-crank levers are coupled by means of a link 43. One arm of the bell-crank lever 39 carries a roller follower engaging a cam 41 on a crank disc 48. Members 3|, 35, 43, 39, 45, 41 may be referred to as coupling means for coupling and decoupling the auxiliary ram 25 relatively to the main ram 5.

The crank disc carries a crankpin 49, whichr forms a coupling with a slot 5| by means of a sliding shoe 53. The slot 5| is located in an oscillating arm or link 55, which is pinned at 51 to the bracket 2| and reaches into the main ram 5 through a slot 59 therein. The end of the arm is slotted, as shown at 6|, to accommodate a pin 63 on the auxiliary ram, so that when the arm 55 is oscillated or cycled relatively to the bracket 2|, the auxiliary ram 25 may be reciprocated relatively to the main ram 5. Parts 53 and 55 may be referred to as cycling means.

The crank disc 48 is attached to a journal 65 rotary in the bracket 2 I. This journal has keyed to it, as shown at 69, a ratchet 61. Rotary on the journal 55 is a control gear 1I which meshes with the stationary rack I1. Pinned to the gear 1| isa pawl 13, which is spring-biased in the usual manner against the ratchet 61. The ratchet carries a notch 15 with which the pawl 13 is engageable. The mechanism 61 and 13 constitutes a one-way clutch between the gear 1I and the crank disc 48. Thus the releasing means for the lock 29, 3| and the operating means 48, 53 and 55 for reciprocating the auxiliary ram 25 are responsive to the upward or retractive movement of the main ram 5, but unresponsive to its downward or advancing movement. Parts I1, 1 I 13, 15 and 61 may therefore be designated as timing.

means.

Operation is as follows, referring to Figs. 1':

and 2:

Assume that the parts start from the position shown in Fig. 1, the crank 1 rotating anticlockwise. The main ram f will, descend, the auxiliary ram 25 then being locked to it by means of the latch 3|. The auxiliary ram 25 is. now

in the most advanced position which it will hold' The punch 21: isy

relatively to the main ram 5. about to enter the draw ring I3. How the shell is inserted (upon the ram operates) will bedescribed later in connection with Fig. 3. The following system of parts then moves downward as a unit, namely; main ram 5, auxiliary ram 25 with the punch 21, andbracket 2|. The locking latch 3| has prior to this been biased by the ef.- fect of gravity on parts 39.' 43 and 35 tolock together rams 5 and 25 so that they move as a unit. The control gear 1I at this time rolls down and the rack I1, being turned thereby anticlockwise relative to the bracket 2|. However, this has no effect at this time upon the lever arm 55, because the gear 1| merely drags the pawl 13. anticlockwise around the ratchet 61 without driving the ratchet. Thus the drawingstroke is accomplished.

When the stated system reaches the bottom of its travel, the main ram 5 is` thereafter raised or retracted. The controlgear thenbegins to rollup the rack I1, its rotation beingv reversed to clockwise movement with respectl to the bracket 2|. This causes the pawl-13V to engage thenotch and turn the ratchet 6.1. Since the latter is keyed at 69 to the journal 65, thel crank disc 48- Then the first action is.

lift of the main ram 5, the rotary system` attached to the gear rotates once, as stated. This oscillates the lever 55 up and'downfrom theposition shown in Fig. 1 (relatively to the bracket 2 I) and back to that position. It will beunderstood that when the lever 55`returnsto its downward angular position after. one, revolution of theY gear, the main ram 5 is approximately. at the top or retractive end of its stroke..

The above points will be clear from a consideration of diagrammatic Fig. 3, whereinl atthe bottom is shown a sequence of positions of the main ram 5, auxiliary ramV and support II. Above this sequence of positions are shown curves of displacement of the rams plotted against, angular positions of the crank 1. In the chart, 0 represents theV crankposition for thelbottommost locationof both rams.. graph of displacement of the main ram 5. Curve A is the curve of displacement ofV the auxiliary ram 25.

Curve. M is theY The letter P diagrammatically illus-- 4 trates a shell to be drawn. Referring to Fig. 3, in the 0 crank position (in this case the lower dead center), both the main ram 5 and the auxiliary ram 25 are in their lowermost positions at the end of the working stroke, beingr latched together at the moment. Whenv the crank has rotated 30 anticlockwise, both rams 5 and 25 are slightly lifted Without having, however, a relative motion, as indicated by the fact that the curves A and M still coincide with one another. Inthe. 60 position, the main ram has moved up more. The auxiliary ram, which partakes of the motion of the main ram has, however, an additional retractive motion in the same direction,

due.: to the, swinging action of the lever 55.

Therefore, at this time the auxiliaryv rain 25 has advanced up inside of the main ram 5. This movement can be traced on the curves A and M by noting. that they separate. In the 90 position, the superimposed accelerating motion of the auxiliary ram 25 on the motion of the main ram 5 can be traced. In approximately the 120 position, the auxiliary ram 25 has been drawn or retracted completely into the main ram 5 (curve Ayapproximately as far above curve M as it will become). During the subsequent travel of the crank between the v and the 180 positions (i. e., during the time that the up or retractive stroke of the main ram 5 is completed) the auxiliary ram 25 is again advanced downward until the two curves A and MH again meet at or about At this time the latch 29 again holds or couples and locks the, auxiliary ram 25 to 'the main ram 5 and the two rams are ready to be pushed down by the remaining action of the crank from the 180 positionto the 360 position. This effects the drawing or working stroke as is clear from Fig. 3, wherein the workpiece P is shown as inserted above the drawing ring I3 at aboutthe 120'positionof the crank. It is applied under the punch 2], which, asY it descends, drives itv throughY the drawing ring I3, as illustrated; In the 360"v position, the shell has been driven entirely through the drawing ring and upon retraction of the punch 21, will be stripped therefrom in the usual manner and dropped.

In Fig. 3, the forward or downward operation between 180 and 360 is illustrated in four steps. These steps show that the drawing operation begins immediately after the crank has passed the upper dead center position, which means that the main ram andtheauxiliaryv ram latched thereto advance slowlyduringl this period under best conditions of reactive moment arm. Therefore,the highestworking pressure which the press has to exert is available right at the beginning of the drawing operation, which means that the pressure' is applied under the-most favorable conditions for the work in. hand. In. other words, a violent punching action isy avoided while a desirableaccelerating` action is obtained.

Moreover, it is clear that thel stroke of the main ram 5 is much shorter for a given amount ofv clearance attained between thepunch 21 and the drawing ring I3.' In other words, the radius of the crank 1 may be about halved. Thus it will be. observedV that the highest pressure to be exerted upon the shell coincides with the beginning of the dra-wingoperation andV with the best position of the crank. Anyy acceleration thereafter occurs duringbutA notV before, the drawing operation. An auxiliary result is. that the press may be operated athigher speeds and with less wear. Moreover the mechanism iscompact and-reliable.

Also, the arrangement of the crank arm of' the crank disc 4B intermediate the link pivots 51 and 63 provides for relatively slow retraction of the auxiliary ram 25 and relatively fast advance of this ram, thereby causing maximum retraction of the auxiliary ram to occur near the end of the return stroke of the slide 5. Thus maximum sp-ace is obtained at the correct time for insertion of the work piece (note the fifth step from the left in Fig. 3 and compare the next two steps).

It will be understood that while I show as an example a particular arrangement of parts providing a main ram drive, coupling means for coupling and decoupling the rams, cycling means for reciprocating the auxiliary ram on the main ram and timing means for coordinating actions to produce the actions illustrated in Fig. 3, equiv aient arrangements of parts may be used.

In view of the above, it will be seen that the several objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above constructions without departing from the scope of the invention, it is intended that all matter contained in the above description or shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. A drawing press comprising a frame, a main ram, a crank and a connecting rod for reciproeating the main ram between extended and retracted positions, an auxiliary ram reciprocating with respect to the main ram from extended to retracted positions with respect thereto, supporting means movable with the main ram, a latch mechanism for locking the auxiliary ram in extended position or unlocking it and carried upon said supporting means, an oscillating link pivoted to the support and having an operative connection with the auxiliary ram, a crank and cam on the support, the crank having a slotted connection with said oscillating link and the cam being operative upon said latch mechanism, a ratchet and pawl device operating said crank and cam, and a gear rotatable on the support for operating said ratchet and pawl and cooperating with a rack on the frame, the ratchet and pawl device being inoperative to drive the crank and cam mechanisms during advance of the main ram but being operative to drive them during retraction of the main ram.

2. A drawing press comprising a frame, a main ram, a crank and a connecting rod for reciprocating the main ram between extended and retracted positions while the crank moves between dead center positions, an auxiliary ram reciprocating with respect to the main ram from extended to retracted positions with respect thereto, supporting means movable with the main ram, a latch mechanism for locking the auxiliary ram in extended position or unlocking it and carried upon said supporting means, an oscillating link pivoted to the support and having an operative connection with the auxiliary ram, a crank and cam on the support, the crank having a slotted connection with said oscillating link and the cam being operative upon said latch mechanism, a ratchet and pawl device operating said crank and cam, and a gear rotatable on the support for operating said ratchet and pawl and cooperating with a rack on the frame, the ratchet and pawl device being inoperative to drive the crank and cam mechanisms during advance of the main ram but being operative to drive them during retraction of the main ram, said gear and rack being designed to effect single cyclic movements of the latch mechanism and the oscillating link duringone retraction of the main ram.

3. A drawing press comprising a frame, a main ram guided on the frame for reciprocation, power means for reciprocating the main ram through working and return strokes, an auxiliary ram guided on the main ram for reciprocation thereon between extended and retracted positions, a latch for locking the auxiliary ram in its extended position, an actuating mechanism carried by the main ram and having a driving contact with the frame so as to be reversibly movable upon reciprocation of the main ram, a member having a one-way driving connection with said reversibly movable actuating mechanism and intermittently driven thereby, a latch release mechanism operatively connecting said driven member and the latch adapted to move the latch to unlock the auxiliary ram upon initial return movement of the main ram, and an additional mechanism connecting said driven member and the auxiliary ram adapted in response to one-way movement of said member to retract and advance the auxiliary ram relative to the mainram during a retractive stroke of the latter.

4;. A drawing press 'comprising a frame, a drawing die supported by the frame, a main ram, a driving mechanism adapted to reciprocate the main ram through working strokes toward the die and retractive strokes from it, an auxiliary ram mounted for reciprocation between advanced and retracted positions on the main ram and carrying a working tool for working cooperation with said die when in said advanced position, releasable coupling means movable to lock the auxiliary ram in said advanced position relative to the main ram and to release it, an actuating mechanism operative by the movement of the main ram and adapted to lock said releasable coupling means during substantially the entire working stroke of the main ram and to release said coupling means during a retractive stroke, means controlled by said actuating mechanism adapted to retract and advance the auxiliary ram relative to the main ram during the retractive stroke of the latter, said actuating mechanism being constituted by a supporting bracket xed to and movable with the main ram, a linkage on said bracket adapted to lock and release said coupling means, an additional linkage on said bracket adapted to eiect said reciprocation of the auxiliary ram on the main ram, and a member 'carried on said bracket engageable with the frame for movement responsive to movement of the bracket, said member coordinately actuating both linkages.

5. A- drawing press comprising a frame, a main ram guided on the frame for reciprocation, power means for reciprocating the main ram through working and return strokes, an auxiliary ram guided on the main ram for reciprocation thereon and with respect thereto between extended and retracted positions, locking means on the main ram and operative in connection with the auxiliary ram for locking the latter in its extended position, an actuating mechanism carried by the main ram and movably cooperating with the frame to lock the auxiliary ram to the main ram throughout said working stroke and to unlock the auxiliary ram during said return stroke, and also to retract the auxiliary ram during an initial part of said return stroke and to advance the auxiliary ram to its extended position during a final portion of said return stroke, said auxillary ramy reciprocating mechanism comprising gear means on the; main ramcooperating with a rack on the frame to assume reversingrotary movements, an actuator which is ratchet driven from said gear means to rotate once upon each return movementrof the main ram, a rst oscillating linkage driven by saidactuator and connected to reciprocate the auxiliary ram during one revolution of the actuator, a second lingage for releasing said locking means at the beginning of eachl retraction of the main ram, and a cam on said actuator and adapted to drive said second linkage during the same revolution of said actua. OI;

6. A drawing, press made according to claim 5, wherein said oscillating linkage comprises an arm pivoted at one end relative to the main ram and connected at the other end to said auxiliary ram, the arm being driven by a crank on the rotary actuator, said crank having a slidingr connection with the arm intermediate said pivot and connection, thereby providing for a relatively slow retraction of the auxiliary ram during a major part ofthe return stroke of the main ram and for relatively fast advance movement during a minor part of saidreturn stroke.

7. A drawing press comprising a frame, a drawing' die supported by the frame, a main ram, a driving mechanism adapted to reciprocate the main ram through Working strokes advancing towardthe die andretractive strokes from it, an auxiliary ram mounted for reciprocation between advanced and retracted positions on the main ram and adapted to carry a working tool for cooperation with said die, coupling means adapted to couple and decouple the auxiliary ram relative to the main ram, cycling means adapted to reciprocate the auxiliary ram with respect to the main ram, and timing means coordinated with movements of the main ram relative to the frame adapted to position said coupling means first to permit coupling of the auxiliary ram to the main ram when the auxiliary ram is in its advanced position relative to the main ram and the main ram is in its retracted position, second to hold coupled the main and auxiliary rams during movement of the main ram toward the die, and third to decouple the auxiliary ram from the main ram only after the main ram starts a retractive movement from the die, said timing means being operative also upon said cycling means to effect reciprocation of the auxiliary ram back and forth relative to the main ram substantially during retractive movement of the main ram from the die.

OTTO HERMANN MAY.

References` Cited. in the le of this patent UNITED STATES PATENTS Number Name Date 455,248 Fennell June 30, 1891 1,443,176 Gabriel Jan. 23, 1923 2,331,490 Menkn Oct. 12, 1943 

